全文获取类型
收费全文 | 396篇 |
免费 | 63篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 8篇 |
综合类 | 30篇 |
化学工业 | 170篇 |
金属工艺 | 25篇 |
机械仪表 | 2篇 |
建筑科学 | 4篇 |
矿业工程 | 3篇 |
水利工程 | 2篇 |
武器工业 | 2篇 |
无线电 | 39篇 |
一般工业技术 | 84篇 |
冶金工业 | 87篇 |
原子能技术 | 1篇 |
自动化技术 | 13篇 |
出版年
2023年 | 11篇 |
2022年 | 19篇 |
2021年 | 23篇 |
2020年 | 25篇 |
2019年 | 27篇 |
2018年 | 26篇 |
2017年 | 35篇 |
2016年 | 15篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 16篇 |
2012年 | 29篇 |
2011年 | 31篇 |
2010年 | 20篇 |
2009年 | 23篇 |
2008年 | 17篇 |
2007年 | 17篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 18篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有470条查询结果,搜索用时 31 毫秒
1.
Photoluminescence properties of Eu-doped WO3-Eu2(WO4)3 composites and single-phase Eu2(WO4)3 powders
《Ceramics International》2022,48(2):1560-1566
The development of highly stable and efficient oxide-based red phosphors is urgently required for next-generation lighting devices. Herein, we report the micro/crystal structures and luminescent properties of single-phase Eu2(WO4)3 and Eu3+-doped WO3-Eu2(WO4)3 composite phosphors prepared by a one-step conventional solid-state reaction method in air atmosphere. As increasing Eu contents in the mixtures of WO3 and Eu2O3, the intensities of the X-ray diffraction peaks of Eu2(WO4)3 increased while that of WO3 decreased. The photoluminescence intensity of the synthesized phosphors increased with increase in the Eu content when calcined at 900 °C, while it degraded at a higher temperature. Red-emitting single-phase Eu2(WO4)3 powders were successfully obtained when the WO3 and Eu2O3 powders were calcined in the ratio of 3:1. The intensity of the red emission spectra of the Eu2(WO4)3 phosphor was higher than those of the 6, 12, and 24 at.% Eu-added WO3 composites at excitation wavelengths of 394 and 465 nm. On the other hand, the intensity of emission from the single-phase phosphor was lower than that of the Eu-doped WO3-Eu2(WO4)3 composites under excitation of UV light at 254 nm. Thus, we propose two prospective phosphors for application as red phosphors at various wavelengths. 相似文献
2.
Yumi Fukuda Ariane Keiko Albessard Iwao Mitsuishi 《Journal of the American Ceramic Society》2019,102(7):4161-4169
The luminescence properties of yellow-emitting Ce3+-doped Sr-containing sialon phosphor Sr(Al,Si)5(O,N)7:Ce3+ were notably improved by the Ce raw material selection. By changing the Ce raw material from oxides to nitrides or chlorides, the emission wavelength shifted to above 560 nm, which is beneficial for higher color rendering index white light-emitting diodes. This result from an increase in the covalency of the host crystal being associated with a decrease in the oxygen content. When Ce chloride was used, both the absorption and internal quantum efficiency increased, resulting in an increase in the external quantum efficiency up to 65%–72%. Inductively coupled plasma mass spectrometry, X-ray diffraction, and electron spin resonance measurements showed that the reason for the absorption increase is an increase in Ce3+ content and suppression of the generation of the second phase, and the reason for the increase in the internal quantum efficiency is a decrease in the host crystal absorption via suppression of anion vacancy generation. It was found that Ce chloride not only suppresses oxygen impurities but also acts as a flux that results in improved crystallinity. 相似文献
3.
Jia Liang Balaji Devakumar Liangling Sun Qi Sun Shaoying Wang Bin Li Daqin Chen Xiaoyong Huang 《Ceramics International》2019,45(4):4564-4569
Novel Mn4+-activated KLaMgWO6 red phosphors with different Mn4+ concentrations were successfully synthesized via a high-temperature solid-state reaction method. The phase formation, microstructure, photoluminescence properties, decay lifetimes and internal quantum efficiency were discussed to analyze the properties of the as-prepared phosphors. The samples belonged to monoclinic crystal system with enough WO6 octahedrons that provided suitable sites for Mn4+ ions. Upon the excitation of 348?nm, KLaMgWO6:Mn4+ phosphors gave bright far-red emission around 696?nm due to the 2Eg→4A2g transition of Mn4+ ions. The critical concentration of Mn4+ was 0.6?mol% and the concentration quenching mechanism belonged to electric multipolar interaction. Besides, the CIE chromaticity coordinates of the KLaMgWO6:0.6%Mn4+ phosphor were (0.7205, 0.2794) which located in deep red range, and its color purity reached up to 96.6%. The KLaMgWO6:0.6%Mn4+ sample also exhibited high internal quantum efficiency of 43%. All of the admirable optical properties indicate that the KLaMgWO6:Mn4+ phosphors can be applied to indoor plant growth illumination. 相似文献
4.
Songhan Hu Zhangwen Long Yugeng Wen Jianbei Qiu Dacheng Zhou Jun’an Lai Dazhao Wang Jiacheng Pi Xizheng Li Qi Wang 《Journal of the American Ceramic Society》2020,103(11):6075-6080
It has been an urgent need for developing a new bright long-wave emitting phosphor to improve the color rendering index (CRI) of white light-emitting diodes (WLEDs). Here, based on the concept of oxygen vacancy-induced long-wave emission by Bi3+ doping, we selected BaSrGa4O8 as the matrix, which has a low-dimensional chain structure that can produce enough oxygen vacancies. After the introduction of Bi3+, orange emission was successfully achieved. To further improve the luminescence efficiency, the system of BaSrGa4O8:Bi3+,K+ was designed. Interestingly, although significant emission enhancement was obtained, the material showed reduced absorption with increased oxygen vacancies. More detailed experimental evidences confirm that oxygen vacancies can activate Bi3+ to achieve long-wave emission. Our results provide a new way to design Bi3+-based long-wave emitting phosphors with low-dimensional crystal structure. Finally, a WLED device containing BaSrGa4O8:Bi3+,K+ was fabricated and exhibited an enhanced CRI, which shows a promising application in WLEDs. 相似文献
5.
Synthesis of blue-emitting AlN:Eu2+ spherical phosphors by carbothermal reduction nitridation method
Sen Li Jie Zhang Zhaobo Tian Xuanyi Yuan Songmo Du Qi Wang Wenbin Cao 《Journal of the American Ceramic Society》2020,103(6):3716-3725
In this study, blue-emitting AlN:Eu2+ spherical phosphors were successfully synthesized for the first time by the carbothermal reduction nitridation (CRN) method, assisted with high nitrogen pressure, appropriate synthesis temperature, and the addition of CaF2. The influence of typical experimental parameters, such as N2 pressure, heating temperature, CaF2 content and Eu2+ concentration on the morphologies and luminescence properties of AlN phosphors were comprehensively investigated. The formation mechanism of spherical morphology were significantly proffered, indicating that sufficient liquid Ca-aluminates during the AlN growth stage were essential for the spheroidization process under the action of surface tension. The synthesized AlN:Eu2+ spherical phosphors presented an intense blue emission band centered in the range of 427- 476 nm relative to the reaction temperature. The lifetime of AlN:Eu2+ phosphor was calculated to be around 1.89 μs. The temperature-dependent PL spectra suggested that the emission band did not shift until 225°C. In addition, the spectral analysis strongly suggested that the luminescence property of AlN:Eu2+ phosphors was significantly enhanced by the large particle size, spherical morphology, reduced impurity content, and appropriate Eu2+ concentration. 相似文献
6.
Neoteric Mn2+-activated Cs3Cu2I5 yellow-emitting halides were achieved by the simple solid-state reaction route. The near-ultraviolet light was the suitable excitation lighting source for the resultant halides. The resultant halides exhibited bright yellow emission under the excitation of 378 nm and the optimum dopant content was 11 mol%. The multipole-multipole interaction contributed to the concentration quenching mechanism and the critical distance was 28.65 Å. The thermal resistance of the prepared compounds was identified by the temperature-dependent emission spectra. Ultimately, the designed light-emitting diode showed bright white light with satisfied color rendering index, proper color coordinate, and suitable correlated color temperature. These results indicated that the prepared yellow-emitting halides were suitable for indoor illumination. 相似文献
7.
Currently, the efficient detection of fingerprints is essential for the crime investigations. Revealing fingerprints is commonly achieved with fluorescent organic compounds but they are not efficient for fingerprint detection on porous or reflective surfaces. In order to solve the problem of collecting fingerprints on porous/reflective surfaces, inorganic phosphors have been employed, since they have characteristics of variable color emission, afterglow, high chemical stability and nano-size, which allow the fingerprint detection on any porous or non-porous surfaces. Due to these last properties, this review presents a summary about the use of phosphorescent and fluorescent phosphors for the detection of latent fingerprints. First, we discussed the main physical and chemical characteristics of the fingerprints which permit their detection and collection from any surface. After this, we presented the main morphological, structural and luminescent properties of the phosphorescent and fluorescent phosphors that allow their use for fingerprint detection. Later, we demonstrated with pictures of fingerprints (with and without light emission from the phosphors deposited on them) that both, phosphorescent and fluorescent phosphors can be used to visualize fingerprints with high resolution and high contrast without interference of the background surface, which is ideal for its collection and registration in the Automated Fingerprint Identification System (AFIS). We believe that this review could be useful to understand how to select an appropriate phosphorescent or fluorescent material for fingerprint detection depending on the type of surface (porous or non-porous, reflective or not reflective) where the fingerprint is deposited. 相似文献
8.
黄朝辉 《广东有色金属学报》2007,1(3):217-220
介绍了国内夜光粉表面包覆技术的现状,并指出了引起夜光粉水解的原因,夜光粉SrAl2O4:Eu,Dy经包覆后在水中浸泡5天仍有1500 mcd/m2的初始亮度,未经处理的夜光粉几乎失去发光性能.经包覆处理后的夜光粉表面有一层连续致密的保护层,大大提高了它的化学稳定性和发光亮度,拓宽了夜光粉的应用领域. 相似文献
9.
Lin Luo Ronghui Liu Yuanhong Liu Weidong Zhuang Yanfeng Li Shaowei Qin 《中国稀土学报(英文版)》2021,39(4):380-385
A series of non-rare earth Mn4+-activated strontium aluminate phosphors Sr4Al14O25:Mn4+co-doped with Sc3+ions were successfully synthesized by a high-temperature solid-state reaction method.XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc34 ions.Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light,and a deep red emission centered at 652 nm with a narrow full width at half maximum(FWHM)can be obtained,which is attributed to the transition2E→4A2of Mn4+ions.In addition,the crystal field strength parameter(Dq)and Racah parameters(B,C)and energies of states were calculated based on experimental data.Moreover,the luminous intensity of Sr4Al14-xSCxO25:Mn4+is enhanced and increased by 60%compared with Mn4+single incorporated sample at x=0.06.A phenomenon of redshift is observed in the excitation spectrum and discussed systematically.Finally,the mechanism of the positive effects with Sc3+ions incorporated into lattice is discussed in detail.All the results suggest that the Sr4Al13.94Sc0.06O25:Mn4+phosphor will become one of the great candidates for backlight of LCD. 相似文献
10.
Tu Ying-Ying Yang Zi-Han Wang Chun-Hao Wang Ting-Wei Lu Fa-Chun 《Journal of the American Ceramic Society》2022,105(8):5240-5251
With high-temperature solid-state reaction method, a series of Lu2Sr(1−x)Al4SiO12:xEu2+ phosphors have been synthesized. With Rietveld refinement method, the crystal structure of Lu2SrAl4SiO12 has been refined. Under the excitation of the ultraviolet and violet band light, Lu2Sr(1−x)Al4SiO12:xEu2+ emits the Eu2+ characteristic blue broadband light. The photoluminescence properties of concentration quenching, emission peak shift, reflectance spectra, and luminescence decay have been investigated. With the structure analyses, the corresponding physical mechanisms have been discussed. With the increased temperature, this phosphor shows well thermal stabilities. For the xEu = 0.06, 0.08, and 0.1 phosphors, the strong anti-thermal quenching performance has been observed. The reason for the anti-thermal quenching of this phosphor has been discussed. The trap capture mechanism may be the suitable physical mechanism to explain the anti-thermal quenching of this phosphor. This phosphor shows the potential applications in the white LED lighting fields. 相似文献